1. Field of the Invention
The present invention relates to inert gas hazard suppression assemblies used to protect areas or rooms such as computer equipment rooms from hazards, and especially fire. More particularly, the invention relates to such systems, as well as pressure modulating inert gas valves forming a part thereof, where multiple high-pressure inert gas cylinders are used, with each cylinder having a valve unit operable to deliver relatively low pressure inert gas at a generally constant pressure throughout a significant period of time during which gas is delivered, thereby providing effective hazard suppression without the need for high-pressure gas handling and distribution equipment or pressure reducing orifice plates that are typical of prior inert gas hazard suppression systems. Each valve unit includes a spring assembly biasing the unit to an open, gas-flow position as well as a gas flow modulating circuit which maintains the gas pressure around the desired output pressure over a substantial part of the gas delivery cycle.
2. Description of the Prior Art
Hazard suppression systems have long been employed for protecting rooms or areas containing valuable equipment or components, such as computer rooms. Traditionally, these systems have made use of one or more of the Halon suppressants. These Halon suppressants are ideal from a hazard suppression viewpoint, i.e., they are capable very quickly suppressing a hazard, can be stored at relatively low pressures, and the quantity of suppressant required is relatively small.
However, in recent years the adverse environmental effects of the Halon has become evident and of considerable concern. Indeed, these issues are so significant that many governmental agencies have banned any further use of Halon. In Europe for example, even existing Halon systems are being replaced by systems using other inert gases such as nitrogen, argon, carbon dioxide and mixtures thereof.
In an exemplary European fire suppression system based on the use of Halon as a suppressant agent, a vessel with a nominal capacity of 150 liters filled with liquified Halon is rated to protect a volume of approximately 17,000 cubic feet. The entire piping of a Halon system need be no more than schedule 40 pipe. Where it is desired to replace a Halon installation with an inerting gas system, or in new installations based on an inerting gas, the standards require that the sufficient inert gas be delivered to a predetermined protected area so that the inert gas occupies approximately 40% by the volume of the room. This lowers the oxygen level within the room to something on the order of 10-15%, which starves the fire of oxygen. At least 95% of the requisite amount of inert gas must be delivered to the protected room in a period of 60 seconds. At the same time, the inert gas preferably should be chosen so that people can be in the room after gas delivery for a period of as much as five minutes.
A European inert gas fire suppression system when configured to replace a previous Halon system or as a new installation having a rating, which is equivalent to the exemplary 17,000 cubic foot Halon protection system referenced above, will require 10 high-pressure inert gas vessels as a replacement for the single Halon vessel. The requirement for a far larger number of inert gas storage vessels in a gas inerting fire suppression system as compared with the storage vessel requirements of a Halon system is because each inert gas vessel must be of significantly greater wall thickness and therefore as a practical matter must be significantly smaller. For example, a typical 80 liter inert gas cylinder will have a wall thickness of about 16 millimeters, be about 25 centimeters in diameter and 190 centimeters in length. The single, in this instance, 150 liter Halon vessel of the example, will be 40 centimeters in diameter and 100 centimeters in length. It is therefore obvious that on the basis that as many as 10 times as many inerting gas vessels are required as compared with a required number of Halon vessels for a particular installation that the space requirements for inerting vessels are much greater.
Because inerting gas is stored as a gas rather than a liquid at very high pressures, e.g., 300 bar, compared with the much lower 25 bar pressure in a typical Halon storage vessel, a manifold pipe must be provided that is connected to all of the inerting gas cylinders, which is capable of withstanding simultaneous release of the high-pressure gas from the storage cylinders for direction of the gas to the piping distribution system of the fire suppression system. The manifold pipe must be at least schedule 160 piping to accommodate the high pressure. A pressure letdown orifice plate is provided at the end of the manifold, which also must be capable of withstanding the 300 bar inerting gas pressure.
Thus, in an instance where an existing Halon system is to be retrofitted using high-pressure inerting gas, not only are a significantly greater number of suppressant agent storage vessels required as explained, but in addition, there is the need for a schedule 160 manifold connected to all of the storage cylinders, and in conjunction with a high-pressure orifice plate to reduce the gas pressure to a level that can be handled by the existing schedule 40 pipe. The schedule 160 pipe needed is manifestly more expensive than schedule 40 pipe and there will be a requirement for approximately 0.3 meters of schedule 160 pipe for each inert gas vessel. Similarly, the same requirement obtained in connection with a new installation.
Accordingly, there is a real and unsatisfied need in the art for improved hazard suppression systems which can make use of relatively low pressure non-Halon inert suppression gas with existing Halon system piping (or low cost, overall low pressure piping in the case of new systems) while at the same time exhibiting the performance characteristics required for rapid hazard suppression.